1. Field of the Invention
The present invention relates to a radiation system for treating patients with certain skin conditions, such as skin cancer; and more particularly, it relates to a low energy or superficial x-ray radiation therapy system equipped with x-ray filters for regulating the characteristics of the radiation.
2. Description of Related Art
The so-called superficial x-rays are low energy x-rays useful for treating certain conditions within a shallow depth of human skin, such as skin cancers and dermatological disorders. A superficial radiation therapy system delivers most of the radiation at or near the skin surface. Superficial radiation therapy is effective for certain patients with basal cell carcinoma, squamous cell carcinoma and Kaposi's sarcoma. These types of cancer can be disfiguring due to the location and surgical scarring. Superficial radiation treatment is simple, painless and significantly less expensive than other alternatives, and it does not leave scarring like surgery.
In superficial radiation therapy treatment, it is very important to insure that the patient receives the correct radiation energy and dose. Commercially available superficial x-ray therapy systems, such as PHILIPS RT.-100, THERAPAX 150 and GULMAY D3150, have an x-ray source with several adjustable energy (in kilovolts) and intensity (in milliamps) levels. For example the PHILIPS RT-100 has settings of 10/8, 20/10, 30/10, 37/10, 45/10, 55/10 70/10, 85/8, and 100/8 kV/mA.
The quality of the X-rays plays a great role in the size of the administered dose. Radiation from a x-ray tube normally has a broad energy spectrum. Higher energy radiation is useful in treating the patient, because it passes through the skin and reaches a certain depth. Lower energy radiation, by contrast, gets stopped near the skin surface. Therefore, it is primarily the low energy radiation that creates unnecessary exposure to the patient. For this reason, a filter, normally made with a metal like copper or aluminum, is placed in front of the X-ray tube. Some low energy radiation is absorbed in the filter plate, and the remaining radiation emerging from the filter has a narrower spectrum. This filtration can also regulate the radiation dose delivered to the patient. In existing superficial radiation treatment systems such as PHILIPS RT-100, there are as many as nine filters in varying materials and thickness, each is used for one particular voltage/current setting of the x-ray tube. A user (operator of the x-ray therapy system) sets up a filter according to the x-ray tube setting, by inserting the filter plate manually. Since an incorrect insertion of a filter could result in improper radiation energy and dose to be delivered to the patient, to prevent this problem, an interlocking mechanism is used in some systems. Once energy/current level is set, only the filter with the correct interlocking notches can be inserted.
In addition to the filters, the x-ray systems are equipped with an x-ray blocker that is a thick piece of heavy metal such as lead. The blocker is normally used during warm-up process of the x-ray tube in order to prevent x-rays from exiting the radiation head. In the existing systems, this blocker is also inserted manually.
What is needed is an automatic filter setting mechanism that selects correct filter (or filter combination) in correspondence to the voltage and current setting of the x-ray system and inserts such correct filter or lead blocker automatically by a command from a central controlling module, controlled by the system user.